netdev - Re: [net-next v2 3/4] openvswitch: Add meter infrastructure

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Date:   Fri, 20 Oct 2017 20:32:44 -0700
From:   Pravin Shelar <pshelar@....org>
To:     Andy Zhou <azhou@....org>
Cc:     Greg Rose <gvrose8192@...il.com>, Joe Stringer <joe@....org>,
        Linux Kernel Network Developers <netdev@...r.kernel.org>
Subject: Re: [net-next v2 3/4] openvswitch: Add meter infrastructure

On Thu, Oct 19, 2017 at 5:58 PM, Andy Zhou <azhou@....org> wrote:
>
> On Thu, Oct 19, 2017 at 02:47 Pravin Shelar <pshelar@....org> wrote:
>>
>> On Tue, Oct 17, 2017 at 12:36 AM, Andy Zhou <azhou@....org> wrote:
>> > OVS kernel datapath so far does not support Openflow meter action.
>> > This is the first stab at adding kernel datapath meter support.
>> > This implementation supports only drop band type.
>> >
>> > Signed-off-by: Andy Zhou <azhou@....org>
>> > ---
>> >  net/openvswitch/Makefile   |   1 +
>> >  net/openvswitch/datapath.c |  14 +-
>> >  net/openvswitch/datapath.h |   3 +
>> >  net/openvswitch/meter.c    | 604
>> > +++++++++++++++++++++++++++++++++++++++++++++
>> >  net/openvswitch/meter.h    |  54 ++++
>> >  5 files changed, 674 insertions(+), 2 deletions(-)
>> >  create mode 100644 net/openvswitch/meter.c
>> >  create mode 100644 net/openvswitch/meter.h
>> >
>> This patch mostly looks good. I have one comment below.
>>
>> > +static int ovs_meter_cmd_set(struct sk_buff *skb, struct genl_info
>> > *info)
>> > +{
>> > +       struct nlattr **a = info->attrs;
>> > +       struct dp_meter *meter, *old_meter;
>> > +       struct sk_buff *reply;
>> > +       struct ovs_header *ovs_reply_header;
>> > +       struct ovs_header *ovs_header = info->userhdr;
>> > +       struct datapath *dp;
>> > +       int err;
>> > +       u32 meter_id;
>> > +       bool failed;
>> > +
>> > +       meter = dp_meter_create(a);
>> > +       if (IS_ERR_OR_NULL(meter))
>> > +               return PTR_ERR(meter);
>> > +
>> > +       reply = ovs_meter_cmd_reply_start(info, OVS_METER_CMD_SET,
>> > +                                         &ovs_reply_header);
>> > +       if (IS_ERR(reply)) {
>> > +               err = PTR_ERR(reply);
>> > +               goto exit_free_meter;
>> > +       }
>> > +
>> > +       ovs_lock();
>> > +       dp = get_dp(sock_net(skb->sk), ovs_header->dp_ifindex);
>> > +       if (!dp) {
>> > +               err = -ENODEV;
>> > +               goto exit_unlock;
>> > +       }
>> > +
>> > +       if (!a[OVS_METER_ATTR_ID]) {
>> > +               err = -ENODEV;
>> > +               goto exit_unlock;
>> > +       }
>> > +
>> > +       meter_id = nla_get_u32(a[OVS_METER_ATTR_ID]);
>> > +
>> > +       /* Cannot fail after this. */
>> > +       old_meter = lookup_meter(dp, meter_id);
>> I do not see RCU read lock taken here. This is not correctness issue
>> but it could cause RCU checker to spit out warning message. You could
>> do same trick that is done in get_dp() to avoid this issue.
>
> O.K.
>>
>>
>>
>> Can you also test the code with rcu sparse check config option enabled?
>
>
> Do you mean to sparse compile with CONFIG_PROVE_LOCKING and
> CONFIG_DENUG_OBJECTS_RCU_HEAD?

You could use all following options simultaneously:
CONFIG_PREEMPT
CONFIG_DEBUG_PREEMPT
CONFIG_DEBUG_SPINLOCK
CONFIG_DEBUG_ATOMIC_SLEEP
CONFIG_PROVE_RCU
CONFIG_DEBUG_OBJECTS_RCU_HEAD

Thanks,
Pravin.